Infections - Soft Tissue - Hand Flashcards

Question

A 53-year-old man returns to the emergency department because he has redness, swelling, and severe pain in the left upper extremity two days after he sustained a laceration to the left hand. Current temperature is 102 °F (38.9 °C) and heart rate is 126/min. Current examination shows crepitus extending into the left forearm. Radiograph shows some gas in the soft tissue. Which of the following is the most likely causative organism? A ) Eikenella corrodens B ) Pasteurella multocida C ) Pseudomonas aeruginosa D ) Staphylococcus epidermidis E ) Streptococcus pyogenes

Answer 1

The correct response is Option E. The most likely causative organism is Streptococcus pyogenes (Group A Strep). Necrotizing soft-tissue infections (necrotizing fasciitis) are rapidly progressive and potentially lethal. Symptoms usually begin with localized erythema and swelling and may mimic cellulitis in the early stages. Severe pain, crepitus, and systemic toxicity can provide clues to the diagnosis. Radiographs may show air in the soft tissues, and patients may exhibit grayish, watery discharge (dishwater pus). These infections can be caused by polymicrobial synergistic infections or may be monobacterial in nature. A recent study showed that group A streptococcus was the most common cause of monobacterial necrotizing fasciitis and that diabetes was the most commonly associated comorbidity. Early intervention and radical debridement are key to management of necrotizing fasciitis. Eikenella corrodens is an anaerobic organism present in human oral flora and has been associated with human bite wounds. Pasteurella multocida is a gram-negative anaerobic bacterium most commonly associated with cat bite infections. Pseudomonas aeruginosa is a gram-negative rod that can be associated with diabetic wound infections. Staphylococcus epidermidis is a gram-positive coccus present on the skin. It has been associated with implant infections. Clostridial and beta streptococcal infections are the most common causes of early-onset necrotizing infection. Diabetes mellitus is the most common morbidity.

Answer 2

The correct response is Option A. Adjunctive treatment in this patient should include antibiotic prophylaxis against Aeromonas hydrophila organisms. This is a symbiotic bacteria found in the intestines of medicinal-grade leeches of the Hirudo medicinalis species, which can be applied to flaps or replanted limbs in order to alleviate venous congestion. The Aeromonas bacteria produces digestive enzymes that act to break down hemoglobin within the intestines of the leech. However, patients with devitalized vascular tissue are particularly susceptible to infection with this gram-negative organism. Affected patients will develop a rapidly progressive infection with gas in the soft tissues that can resemble clostridial myonecrosis. Appropriate management consists of debridement of the affected area and administration of aminoglycoside, trimethoprim-sulfamethoxazole, or a third-generation cephalosporin. Eikenella corrodens is a facultative anaerobic gram-negative rod typically associated with human bite wounds. Penicillin or ampicillin is recommended for treatment. Histoplasma capsulatum is a fungus that results in arthralgia and arthritis in affected patients. Administration of amphotericin B is indicated. Pasteurella multocida is an anaerobic gram-negative bacillus, typically associated with cat bites and best treated with penicillin or amoxicillin with clavulanate. Staphylococcus aureus is an anaerobic gram-positive coccus present on the skin that is a frequent cause of skin and soft-tissue infections.

Answer 3

The correct response is Option C. Given the patient’s history of diabetes and necrotizing non-purulent infection after minimal trauma, he is likely to have mucormycosis, a life-threatening fungal infection caused by organisms from the class Zygomycetes. On microscopy, tissue samples from patients with mucormycosis demonstrate right-angle nonseptate branching hyphae. Grape-like clusters of gram-positive bacteria is not appropriate. This option describes the characteristic appearance of a staphylococcal infection. Given the patient’s lack of cellulitis or purulent infection, it is an unlikely mechanism for this necrotizing ulceration. Septate nonbranching hyphae and yeast forms is not appropriate. This option describes the characteristic appearance of a candidal infection. Given the patient’s lack of marked erythema and excoriation, and location of the infection on the face, rather than in skin folds, the likelihood of Candida as the primary pathogen is extremely low. Chain-like collections of gram-positive bacteria is not appropriate. This option describes the characteristic appearance of a streptococcal infection. Although streptococcal infections are common in the head and neck region, the patient’s history and appearance of the lesion do not support Streptococcus as the causative organism. Tiny yeast forms with occasional unequal bud formation is not appropriate. This option describes the characteristic appearance of Histoplasma capsulatum, an opportunistic fungus, which may cause marked pulmonary infections in immunocompromised patients. Often emergent debridement is required, and that decision will need to be made on Gram stain, not on final culture.

Answer 4

The correct response is Option E. The patient described has necrotizing fasciitis and sepsis. Vibrio vulnificus is a gram-negative bacillus, a cause of necrotizing fasciitis, and is commonly associated with warm saltwater environments (Florida). It also tends to present with hemorrhagic bullae. Staphylococcus aureus is a gram-positive coccus, is not associated with watery environments, and is more commonly associated with pustules rather than hemorrhagic bullae. Clostridium perfringens is a gas-forming, gram-positive bacillus, and is associated with marine sediment. Pseudomonas aeruginosa, also a gram-negative bacillus, although associated with moist environments, is more typically associated with less aggressive soft-tissue infections. Mycobacterium marinum is also associated with watery environments, but tends to affect aquarium owners with an indolent granulomatous process.

Answer 5

The correct response is Option B. Oral metronidazole is the most appropriate treatment for this patient with a mild/moderate form of Clostridium difficile infection. Oral vancomycin is recommended for treatment of those with severe disease, or with mild/moderate disease who did not respond to metronidazole. Patients who cannot tolerate oral medications (eg, postoperative ileus) or who have an intestinal diversion (eg, ileostomy) can be treated with intravenous metronidazole or with vancomycin enemas. Vancomycin is not excreted into the colon and therefore should not be given intravenously to treat C. difficile infection. Oral fidaxomicin has been shown to be as effective as oral vancomycin in the treatment of C. difficile infections. Although further clinical experience is still needed, this drug has been associated with increased cure rate in patients receiving concomitant antibiotics and decreased infection recurrence when compared to vancomycin. Teicoplanin and rifaximin are not generally recommended for treatment of C. difficile, although isolated reports of successful therapy can be found in the literature.

Answer 6

The correct response is Option E. Given the obvious devitalized tissue in the associated photograph, the most appropriate next step would be further debridement. This is an often overlooked, but still critical, cornerstone to reconstruction, because without it, complication rates from infection are significantly increased. Debridement involves the removal of nonviable or contaminated tissue that impedes normal tissue growth. It renews the wound and surrounding tissue to promote normal healing by removing infection, biofilm, and senescent cells. Different debridement options are available, including mechanical, biologic, technical, and surgical methods. In this acute scenario with an otherwise healthy patient and a large amount of devitalized tissue, surgical debridement is the most appropriate choice. All other modalities/choices are not appropriate until the wound bed is stabilized. Negative pressure wound therapy may be used in conjunction with debridement, but is not a replacement for it.

Answer 7

The correct response is Option C. For the patient described with a penicillin or cephalosporin allergy, trimethoprim-sulfamethoxazole (TMP/SMX) and clindamycin or metronidazole, or a fluoroquinolone and clindamycin or metronidazole, are good antibiotic therapy combinations. Cat bites account for 5 to 15% of animal bites and occur more often in women and adults (median age is 20 years). Most cat bite injuries occur on the upper extremity with 'scratches' on the finger or hand. Infection rates after cat bites range from 50 to 75%. This is typically attributed to the fine, sharp teeth of cats, which produce puncture wounds and penetrate deeply into the soft tissues and joint capsules of the hand. Wounds to the hand demonstrate an increased risk of infection; closed fist injuries have the highest risk. Initial medical management of bite wounds includes ascertaining the rabies status of the animal and updating the tetanus immunization of the patient if necessary. If rabies is suspected, irrigation with povidone-iodine solution will reduce the development by up to 90%. A careful examination of the affected hand/extremity should address the surrounding soft tissues and potential spaces of the hand, tendons, joint and joint capsules, and underlying bone. The wound should be irrigated with saline after obtaining wound cultures. Necrotic tissue should be debrided, and any cat bite with worsening pain will require incision and irrigation of the puncture site. All cat bite wounds should be left open, although large gaping wounds can be loosely approximated. Before definitive surgical treatment of any associated abscess or debridement of devitalized tissue, empiric antibiotic therapy should be started. The majority of cat bite wounds are polymicrobial and the anaerobic organisms are often overlooked. Common aerobic pathogens include Staphylococcus aureus, viridans streptococcus, Corynebacterium, Pasteurella multocida, and various gram-negative enteric organisms. The most common anaerobic pathogens include Bacteroides, Fusobacterium, Peptostreptococcus, and Actinomyces species. Pasteurella multocida, an aerobic, facultative anaerobic gram-negative pathogen, is the most commonly isolated pathogen in cat bites and is present in up to 50% of infected wounds. Symptoms of Pasteurella multocida infection develop rapidly within 24 hours and typically include cellulitis and seropurulent drainage. Other uncommon infections have been reported after cat bites, including tularemia (Francisella tularensis) and cat-scratch disease (Bartonella henselae). Patients with severe wounds (crush injury, joint involvement, deep space infection), cellulitis, sepsis, diabetes, immunosuppression, or other high-risk factors for treatment failure should receive parenteral antibiotics. Alternatives to amoxicillin and clavulanate potassium or ampicillin and sulbactam include other penicillins or cephalosporins, provided they display adequate anaerobic coverage. In the scenario described, the choices containing amoxicillin, ampicillin, and cefazolin are not appropriate because of the patient’s penicillin allergy. Additionally, this patient will require intravenous antibiotics because of the wound severity, so amoxicillin and clavulanate potassium would not be appropriate. The combination of tetracycline and TMP/SMX alone does not provide adequate anaerobic coverage.

Answer 8

The correct response is Option C. The patient described has a severe, necrotizing soft-tissue infection, as suggested by tenderness and swelling of the entire limb compartment. Urgent debridement is required. Necrotizing fasciitis must be suspected in any patient with a compromised immune system, even when he or she has a relatively small surface wound. The infection spreads along deep tissue planes €”in this scenario, the muscle fascia. Severe inflammation may result in elevated compartment pressures, requiring fasciotomy. Intraoperative bacterial cultures should guide specific antibiotic therapy. Patients with severe continued or extensive necrosis may benefit from hyperbaric oxygen (HBO) therapy. After all of the necrotic tissue is removed, vacuum-assisted compression (VAC) dressings may be applied to expedite granulation. Definitive closure may involve healing by second intention, skin grafts, or flaps as clinically indicated.

Answer 9

The correct response is Option A. Cat and dog bite infections have a complex microbiologic mix, with Pasteurella as the most frequent isolate. Common aerobes isolated include streptococci, staphylococci, Moraxella, and Neisseria; common anaerobes include Fusobacterium, Bacteroides, Porphyromonas, and Prevotella. Patients are most often treated with a combination of a β-lactam antibiotic and a β-lactamase inhibitor, such as amoxicillin and clavulanic acid. Alternative treatments include clindamycin plus fluoroquinolone for adults and clindamycin and trimethoprim/sulfamethoxazole for children. Ciprofloxacin does not provide adequate coverage for expected pathogens. In general, cat bites tend to be small puncture wounds that seal almost immediately; thus, wounds should be opened sufficiently to be cleaned and allowed to drain. Dog bite wounds tend to be longitudinal lacerations that are more likely to stay open by themselves. However, canine lacerations, as compared to cat bite punctures, are more likely to result in direct structural damage to nerves, tendons, vessels, and joint structures. Rabies is uncommon in dogs and cats in the United States. Because the cat owner is known, the vaccination record is obtainable. An animal that appears healthy and has been vaccinated should still be quarantined for 10 days to ensure it does not show signs of rabies. If the animal is found to have rabies, postexposure prophylaxis should be started as soon as possible. If the animal is a stray, the animal should be located so it can be tested for rabies. If, however, the animal cannot be located, postexposure prophylaxis is reasonable. Administration of tetanus immune globulin is recommended only for patients with tetanus-prone wounds who have never completed a primary immunization series. If a patient with an acute soft-tissue injury has not been immunized previously, a tetanus toxoid booster is required. The patient must complete the series. If the patient has been immunized previously, a booster dose is given if the last dose was more than five years previously (for a tetanus-prone wound) or more than 10 years previously (for a nontetanus-prone wound). Patients with a contraindication to tetanus toxoid must be managed with tetanus immune globulin alone. Observation alone would not be appropriate for a deep puncture wound with purulent drainage and a mildly elevated leukocyte count. After adequate drainage of the wound and treatment with oral antibiotics, the patient requires follow-up to ensure the infection does not progress, possibly requiring intravenous antibiotics and further surgical drainage.

Answer 10

The correct response is Option B. Rhinocerebral mucormycosis is a rare opportunistic infection of the sinuses, nasal passages, oral cavity, and brain caused by saprophytic fungi. The infection can rapidly result in death. Rhinocerebral mucormycosis commonly affects individuals with diabetes and those in immunocompromised states. The diagnosis of mucormycosis is established by obtaining a biopsy specimen of the involved tissue, and frozen tissue samples should be immediately evaluated for signs of infection. Microscopic characterization of non-septate hyphae, rhizoids, columellae, sporangia, and sporangiospores helps to define genus and species within the order Mucorales. Optimal therapy requires a multidisciplinary approach that relies on prompt institution of appropriate antifungal therapy with amphotericin B (AmB), reversal of underlying predisposing conditions, and, where possible, surgical debridement of devitalized tissue. Surgery should be considered early, and if possible, emergently with the goal of removing all necrotic tissue. Repeated debridements are frequently necessary and the extent of surgery should ideally be guided by evaluation of frozen tissue sections examined histologically. In the scenario provided, orbital involvement will most likely require sacrifice of the eye.

Answer 11

The correct response is Option E. The patient has a history and physical findings consistent with herpetic whitlow. This is a viral infection caused by herpes simplex virus and is more common in medical and dental personnel. Tzank smear or antibody titers can confirm a diagnosis but are unnecessary in the management of this patient. Treatment is primarily nonoperative and involves observation, as the course of the illness is self limiting with resolution in 1 to 3 weeks. Intravenous antibiotics would not treat this viral infection. Incision and drainage is unnecessary and may lead to a bacterial superinfection or systemic dissemination of herpes simplex virus. Acyclovir or valacyclovir may shorten the duration of symptoms, but must be started within 2 to 3 days of onset. Topical application of an antimicrobial would provide no benefit in this case. Surgical drainage of the bullae should not be performed because it may increase the risk of spreading the herpes virus and may also lead to bacterial superinfection.

Answer 12

The correct response is Option E. The most appropriate prophylactic regimen to prescribe in this clinical scenario is trimethoprim-sulfamethoxazole and clindamycin. Dog bites to the hand are potentially dangerous bites that could lead to serious hand infections. The common microorganisms that cause infections in such bites are Pasteurella species, anaerobes, Staphylococcus aureus, and Streptococcus. The ideal antibiotic would have been amoxicillin-clavulanic acid, which covers most of these microorganisms. However, the child is allergic to penicillin, and, therefore, this drug is contraindicated. Another good option would have been amoxicillin and clindamycin (for the anaerobic coverage). However, for the same reason described above, it too cannot be used. Tetracyclines are contraindicated in children under 8 years of age owing to the ill effects on growing teeth and bones. Quinolones are also contraindicated in children under 18 years of age owing to their harmful effects on cartilage and joints. Although this is debatable, currently the use of quinolones in children is restricted by the Food and Drug Administration to certain specific conditions (cystic fibrosis, multidrug-resistant urinary tract infection, and inhalational anthrax). Clindamycin alone does not adequately cover most of the organisms involved, including Pasteurella, which is gram-negative.

Answer 13

The correct response is Option E. This patient has developed infection with Aeromonas hydrophila after undergoing leech therapy for five days. Medicinal leeches such as the Hirudo medicinalis species (which is the most commonly used leech and is endemic to Southeast Asia and Europe) can be applied to flaps or replanted limbs in order to relieve venous congestion. However, a common complication of leech therapy is the development of infectious organisms such as Aeromonas hydrophila, a gram-negative rod that can be detected in as many as 20% of persons within the first 10 days of therapy. Infiltration of Aeromonas hydrophila organisms can result in a rapidly progressive infection with gas in the soft tissues that can resemble clostridial myonecrosis. If infection does develop, trimethoprim-sulfamethoxazole is recommended for first-line therapy. Fluoroquinolones such as ciprofloxacin are also effective. Antibiotics that are still effective but less frequently recommended include antipseudomonal aminoglycoside, imipenem, meropenem, tetracycline, and second-, third-, or fourth-generation cephalosporins.

Answer 14

The correct answer is option C. The diagnosis is consistent with necrotizing fasciitis with an isolate of group A strep. The primary treatment includes adequate debridement, resuscitation and metabolic support. **Pencillin** is appropriate for treating the infection and clindamycin is beneficial to the resuscitative process. Large incolums of group A Strep cause significant muscle injury due to toxin production. **Clindamycin** prevents protein toxin synthesis at the ribosomal level. It also suppresses the growth of pencillin binding proteins.

Answer 15

The correct response is Option A. Tuberculosus tenosynovitis is the most frequent tuberculosus infection in the hand. It may clinically simulate rheumatoid tenosynovitis. The most common pathogen is Mycobacterium marinum. Radiographs often show no abnormalities and pathology alone will often show only nonspecific tenosynovitis, but granulomas may be present. Cultures must be requested at 30 degrees Celsius to identify M. marinum. There are several diagnostic clues for tuberculous tenosynovitis, such as proliferative synovitis occurring in the absence of a known rheumatoid or collagen vascular disease as well as the presence of rice bodies during surgical exploration. Rice bodies are infected villous bodies on the synovial surface that break off and become trapped within the inflammatory mass. CT scan of the abdomen is sometimes recommended for women with palmar fibromatosis and arthritis because this condition may be associated with ovarian cancer. Amyloidosis can cause tenosynovitis and carpal tunnel syndrome but does not commonly produce rice bodies. Allopurinol is a treatment for gout, and potassium hydroxide stains are used to identify fungus.

Answer 16

The correct response is Option B. The patient described has an occupation that exposes him to contaminated water and raw seafood. Infections from Mycobacterium marinum and Vibrio vulnificus are both possible. Mycobacterium marinum is the most common atypical mycobacterium seen in hand infections, often seen after penetration by aquatic equipment, colonized marine life, or contact with contaminated water. The most common deep infection is flexor tenosynovitis, and may present as a chronic tenosynovitis. Sporothrix schenckii is a fungus found in plants and soil. Inoculation with the pathogen results in a papule at the entry site, followed by development of lesions along the lymphatic chain. Suppurative flexor tenosynovitis typically presents with pain over the tendon sheath, semiflexed position of the involved digit, pain on passive extension, and symmetrical swelling of the finger. This classic presentation is commonly caused by pathogens such as Staphylococcus aureus or Eikenella corrodens (often seen in association with human bite injuries). In tenosynovitis infections involving atypical mycobacterium, however, there is absence of pain. Vibrio vulnificus is a species of gram-negative, motile, curved bacterium found in the coastal waters of the United States. Infections from V vulnificus may be caused by direct exposure of an open wound to warm seawater containing the organism or from handling raw seafood or marine wildlife. Infections caused by V vulnificus result in painful cellulitis that progresses rapidly and presents with marked local tissue swelling with hemorrhagic bullae. Bacteremia with systemic symptoms is commonly seen.

Answer 17

The correct response is Option E. Staphylococcus aureus and viridans streptococcus are the two most commonly isolated organisms in hidradenitis suppurativa. As a result, initial management should include empiric administration of antibiotics effective against these organisms until the results of cultures are received. Hidradenitis suppurativa is a condition that is poorly understood but is thought to result from chronic infection of the apocrine sweat glands. Although the axillae are affected most commonly, the perineum, groin, and genitalia may also be involved. Extensive scar tissue and fistula tracts develop over time, and the condition becomes progressively more difficult to treat. In patients with hidradenitis, appropriate management is application of warm compresses, incision and drainage of the appropriate areas, and administration of antibiotics. Patients with more severe cases should undergo excision of the involved skin and subcutaneous tissue followed by coverage with a local flap or skin graft. Investigational studies of a method of immunotherapy, based on the staphylococcal phage lysate vaccine, have shown promising results in patients with chronic hidradenitis suppurativa.

Answer 18

The correct response is Option E. The CDC defines a surgical site infection as an infection that occurs at the incision site or within the organ or space operated on within 30 days after surgery or within 1 year if a prosthetic implant is placed. Infection requires at least one of the following: Purulent drainage from the surgical site Organisms isolated from an aseptically obtained culture of fluid or tissue at the surgical site Spontaneous dehiscence of a deep incision or deliberate opening of the incision by a surgeon when the patient has at least one of the following signs or symptoms: fever (greater than 100.4°F [38.0°C]), localized pain or tenderness, localized swelling, redness, or heat, unless site is culture-negative An abscess or other evidence of infection involving the incision or operative site that is found on direct examination, during reoperation, or by histopathologic or radiologic examination Diagnosis of a surgical site infection by a surgeon or attending physician

Answer 19

Correct answer is option C. When disseminated to the hand, *coccidiomycosis* usually presents as tenosynovitis in adults and osteomyelitis in children. Anywhere from 100 to 500 new disseminated cases per year come from *Arizona, New Mexico, and surrounding area*. *The Mississippi & Ohio River valley* is endemic for both *blastomycosis and histoplasmosis*. Most patients with blastomycosis present with skin lesions, typically to the dorsum of the hand, and histoplasmosis may present as flexor tenosynovitis. *Sporothrix schenckii* is a ubiquitous soil saprophyte, which is not restricted to northern latitudes but often encountered among farmers, gardeners and florists. Distal puncture wounds cause local subcutaneous nodules that may ulcerate. More proximal lesions appear along lymphatic channels over a course of several weeks. Bone involvement does not usually occur in sporotrichosis. Chromomycosis represents infections from five genera of dematiacious fungi, which typically cause superficial mycosis of the upper extremities in the tropics.

Answer 20

The correct response is Option C. The venom of the black widow spider (Latrodectus mactans) is a neurotoxic agent that causes the hallmark findings of muscle pain and cramping that appear within 15 minutes after the bite. This common species of spider is found throughout the United States. Most patients with latrodectism are bitten by female spiders; in contrast, the bite of the male spider rarely penetrates the skin. Affected patients have sharp pain at the wound site with two small red spots marking the location of puncture. Late findings include pain and cramping of the striated muscles, abdominal pain, vomiting, tremor, excessive salivation, and shock. In a patient who is bitten by a black widow spider, the most appropriate therapy is administration of 10 mL of 10% calcium gluconate solution over a period of 15 to 20 minutes; 1 ampule of methocarbamol or 5 mg to 10 mg of diazepam can be administered additionally. Improvement of the patient's symptoms following treatment is diagnostic of latrodectism. In immunocompromised patients, a diluted dose of black widow spider antivenin (Lyovac) should be administered intravenously at a slow rate. In contrast, the brown recluse spider produces a toxin known as sphingomyelinate, a dermonecrotic factor. Envenomation with sphingomyelinate results in hemolysis, coagulation, and platelet aggregation, often affecting fatty tissue. Symptoms can range from mild irritation to severe necrosis. Hemotoxins, such as cobra venom, are exotoxins that result in hemolysis.

Answer 21

A) Administration of acyclovir

Answer 22

The correct response is Option C. Orbital cellulitis may be caused by local extension of a superficial infection such as a hordeolum, or from adjacent infected sinuses, or by hematogenous seeding from a dental or facial abscess. It is important to distinguish between preseptal and orbital cellulitis, which should be suspected when unilateral proptosis is present, and to identify the presence of an intraorbital abscess. Infection within the orbit has implications for management and prognosis due to the effect of high mechanical pressures generated in an unyielding compartment, which will manifest as proptosis, and other symptoms including diplopia, ophthalmoplegia, and chemosis. Orbital cellulitis requires hospitalization and prompt initiation of parenteral antibiotics. An intraorbital abscess can form if treatment is delayed, further compounding the intraorbital pressure and causing tissue necrosis. An intraorbital abscess requires immediate surgical drainage due to risk of blindness. Preseptal cellulitis is an infection of periorbital tissues superficial to the orbital septum, and if the source is from a nearby superficial skin infection, then initial management may be done with oral antibiotics and close follow-up. Preseptal cellulitis from a hematogenous source is more likely to become complicated with orbital cellulitis and abscess if it is not managed with parenteral antibiotics. Infections inside the orbit may extend to the central nervous system and may also cause cavernous sinus thrombosis. CT scan or MRI will confirm intraorbital infection, and related sources such as a facial or dental abscess or a sinusitis, and can direct the surgeon to areas requiring surgical drainage. Blood cultures are useful in identifying the causative organism of the infection during periods of bacteremia, and are an appropriate test in the general workup of the patient; however, blood cultures alone do not diagnose or exclude intraorbital infection. Cell counts are also useful in the general workup of the patient to characterize the systemic impact of the infection, and to be used as a guide in the responsiveness to treatment. The counts do not diagnose or exclude intraorbital infection specifically. On Waters view x-ray studies, increased facial or eyelid edema may be seen as a slight diffuse opacification, but they are unable to delineate orbital and periorbital soft tissues individually. Sinus opacification can be suggestive of active sinusitis and a potential cause of orbital cellulitis. In general, plain x-ray study offers far less information than CT scan or MRI and is not diagnostic of intraorbital infection. Wound swabs are helpful in identifying the causative organism of the infection when there is an obvious source, and are an appropriate test in the general workup of the patient; however, wound swabs alone do not diagnose, exclude, or characterize the extent of intraorbital infection.

Answer 23

The correct answer is option D. The lesion demonstrated represents **pyoderma gangrenosum**, which is a cutaneous lesion manifested by skin ulceration and necrosis. The onset is acute and rapid, affecting adults 25–54 years of age. In 30%–60% of cases there is an association with ulcerative colitis. It is much more common in the lower extremity and somewhat rare in the hands. Because of the unusual nature of the lesions, appropriate treatment is often delayed. Treatment is supportive including local wound care and sometimes the use of steroids, dapsone or cyclosporine. Surgical debridement may actually cause the lesions to proliferate. Skin grafting is occasionally needed, but never done during active disease. Treatment of the ulcerative colitis, when present, will also help to resolve the lesions. The etiology is not infectious, hence antibiotic therapies are not helpful.

Answer 24

The correct response is Option D. Infections of the head and neck should not be ignored, as many of them can evolve into life-threatening emergencies, some of them very quickly. Rhinocerebral mucormycosis is a rare opportunistic infection of the nasal cavity and sinuses that can rapidly spread to the orbits and brain by erosion of bone and invasion of blood vessels. Mucormycosis is caused by saprophytic fungi, and usually affects individuals with diabetes mellitus and those who are immunocompromised. The mainstay of treatment includes reversal of immunosuppression when possible, systemic antifungals, and surgical debridement. Timely treatment is critical and usually dependent on rapid diagnosis by history and physical examination, imaging, and intraoperative biopsy with frozen section pathology, since waiting for cultures causes unnecessary delay in severe cases. Mucormycosis can also present in the oral cavity, lungs, ears, and other sites less commonly. Epiglottitis is an infection of the supraglottic region causing inflammation and swelling of the epiglottis. It is most commonly caused by Haemophilus influenzae type b and has become rare since the introduction of the vaccine against this bacteria. Swelling of the epiglottis can cause airway obstruction. Mastoiditis is infection of the mastoid air cells, which are in continuity with the middle ear. The mastoid process behind the ear is also usually swollen and tender. Infections usually start from untreated otitis media. Risks include spreading to the surrounding structures, including the brain. Necrotizing fasciitis is a soft tissue infection that rapidly spreads through the subcutaneous fat and fascia with necrosis of the overlying skin. In the head and neck, the infection is usually spread from infection of the teeth or pharynx. The plaque-like infection of candidiaisis does not present in this fashion.

Answer 25

The correct response is Option C. The radial and ulnar bursas are connected through the Parona space, which lies between the pronator quadratus fascia and the flexor digitorum profundus tendon sheath. The flexor tendon sheath of the small finger often connects with the ulna bursa, which extends proximal to the transverse carpal ligament. This connection can give rise to a €œhorseshoe abscess. € This abscess results when an infection starting in the thumb or small finger progresses proximal through the wrist and then into the opposite flexor tendon sheath through the Parona space. The Parona space can be explored by performing an extended carpal tunnel release. Another potential space in the hand is the thenar space, which is bordered ulnarly by the vertical septum between the flexor sheath and metacarpal of the long finger, dorsally by the fascia of the adductor pollicis, and radially by the thenar muscle fascia. It should be noted that this space does not include the thenar muscles. The midpalmar space is bordered radially by the vertical septum between the flexor sheath and metacarpal of the long finger, dorsally by the fascia over the interossei of the third and fourth web spaces, ulnarly by the fascia over the hypothenar muscles, and volarly by the flexor tendons. The posterior adductor space is defined as the space dorsal to the adductor pollicis and volar to the first dorsal interosseous. The dorsum of the hand contains the posterior interosseous space, which is dorsal to the first dorsal interosseous. The ring finger would be explored if the patient had displayed signs of tenosynovitis of this digit.

Answer 26

The correct response is Option D. In this patient who has septic arthritis affecting the proximal interphalangeal joint of the index finger, the most likely cause is infection with Staphylococcus aureus organisms. Staphylococcus aureus is an anaerobic gram-positive coccus that is present on the skin and is a frequent cause of skin and soft-tissue infections. It is the most common cause of septic arthritis of the hand and wrist. Eikenella corrodens, an anaerobic gram-negative rod, is present in the human mouth and is more likely to be cultured from a human bite wound. Septic arthritis resulting from Neisseria gonorrhoeae is more likely to occur in young men who are sexually active. Affected patients typically have a history of migratory polyarthralgia. Serratia species are a frequent cause of infection in persons who abuse intravenous drugs as well as patients with diabetes mellitus or immune system compromise. Streptococcus species, including viridans streptococcus, are the second most common causative organism in patients with septic arthritis of the hand.

Answer 27

The correct response for Item 198 is Option B and for Item 199 is Option E. Septic arthritis may result from extension of an adjacent subcutaneous abscess or by intra-articular contamination caused by a laceration or puncture wound. The joint is a poorly vascularized potential space, favoring colonization. Early diagnosis and drainage are crucial to treatment, as a joint infection can progress rapidly to destruction of articular cartilage. The two most common organisms that cause hand infections are Staphylococcus aureus and B €‘hemolytic streptococci. Minor staphylococcal and streptococcal infections are treated with first-generation cephalosporins. More significant infections of the interphalangeal joint should be performed through a midaxial incision. Neisseria gonorrhoeae usually manifests as a primary venereal infection. However, it can disseminate and sometimes present as a secondary hand infection, which is often confused with a purulent tenosynovitis or arthritis. It is important to distinguish gonococcal from pyogenic infection because, unlike a pyogenic infection, a gonococcal infection does not usually destroy tendon or articular cartilage. Therefore, incision, drainage, and debridement are unnecessary and should be avoided. Disseminated gonococcal infection is the most common cause of acute infectious arthritis in sexually active adults. A history or evidence of trauma are lacking. Fluid aspiration with Gram staining for gram €‘negative diplococci allows definitive diagnosis. Hospitalization and intravenous administration of a third €‘generation cephalosporin is recommended. Manifestations of Sweet syndrome can masquerade as acute hand infections. Sweet syndrome, originally described as an acute febrile neutrophilic dermatosis, belongs to a class of skin lesions that histologically have intense epidermal and/or dermal inflammatory infiltrate of neutrophils without evidence of infection or vasculitis. The lesions can erupt at sites of minor trauma. The clinical picture is consistent with infection initially. The unresponsiveness of these lesions to antimicrobial therapy and the lack of associated cellulitis is a clue to the diagnosis. The treatment of choice involves a tapering dose of corticosteroids. Herpetic whitlows are often confused with paronychia or felon and are treated mistakenly as such. Initial signs include intense pain and erythema of the fingertip, followed by edema and tenderness. A Tzanck smear of vesicular fluid may show multinucleated giant cells. Primary herpes simplex infections typically resolve without treatment within three weeks. Incision and drainage of herpetic whitlow is contraindicated because surgical treatment converts a closed wound to open and may result in a secondary bacterial infection or viral superinfection. To date, there have been no controlled studies that assess the efficacy of acyclovir for the treatment of herpetic whitlow, but case reports suggest that it both suppresses and decreases the length and severity of recurrent infections when taken orally.

Answer 28

The correct response is Option E. The patient described has signs and symptoms of a rapidly progressive and advancing soft-tissue infection, which is characteristic of necrotizing fasciitis. The treatment of choice is prompt operative debridement and excision of infected soft tissues and fascia. Necrotizing fasciitis is commonly polymicrobial; Group A hemolytic streptococcus and Staphylococcus aureus are the most common offending agents, although other aerobic and anaerobic bacteria are frequently involved. The infection travels along fascial planes and induces local hypoxia and profound overlying soft-tissue necrosis. Patients with necrotizing fasciitis often require repeat debridements early in the course of treatment to limit the spread of infection. Obtaining blood cultures, adding antifungal antibiotics, elevation, and ice compression do not directly address the surgical emergency of necrotizing fasciitis and would potentially delay treatment. Increasing the dosage of intravenous antibiotics would have little effect on the progression of necrotizing fasciitis. Fasciotomy of compartments is useful for a case of compartment syndrome, but not necrotizing fasciitis.

Answer 29

The correct response is Option B. This young patient has limited, focal disease that has failed medical management. Local excision is useful for isolated, scattered individual, or linear lesions. More extensive disease that occupies a significant portion of the skin area may be better treated by complete axillary excision. In this younger patient with limited disease, direct excision of the affected areas is a less morbid approach. Negative pressure wound therapy and skin grafts may be optimal coverage treatments for extensive disease, and some local flaps have been described as well. This stubborn disease originates from the apocrine glands and can often be chronic and disabling. The axillae, groin, perineum, and submammary areas can all be affected. Initial treatments include local care, antibiotics, hygiene, and weight loss. Steroid injections may help in early, small lesions, but have limited effectiveness and are painful. After a 6-week course of antibiotics, this patient is not likely to benefit from more treatment. Only excision of the diseased apocrine glands is likely to be effective. Incision and drainage is a suitable treatment for a closed abscess associated with hidradenitis, but incising this patient's lesions would not improve her situation.

Answer 30

The correct response is Option D. Infections of the index finger drain from the flexor sheath proximally into the thenar space. Infections of the long, ring, and small fingers drain into the midpalmar space. The radial and ulnar bursae communicate by Parona’s space, which lies deep to the pronator muscle.

Answer 31

The correct response is Option A. Cat bites usually result in puncture wounds because of their long, slender, sharp teeth. It has been reported that as many as 80% of cat bites become infected. Pasteurella species are the most common, occurring in as many as 75% of cat bite infections. Other types of bacteria can also be involved as well, including Streptococci, Staphylococci, and anaerobes. Appropriate antimicrobial treatment for bite wounds must take into account the usual bacteriology of these infections. Pasteurella species are susceptible to penicillin, ampicillin, second- and third-generation cephalosporins, doxycycline, trimethoprim-sulfamethoxazole, fluoroquinolones, clarithromycin, and azithromycin, but are resistant to cephalexin, dicloxacillin, erythromycin, and clindamycin. Appropriate choices for prophylaxis and treatment of cat bite wounds would include amoxicillin and clavulanate or a combination of penicillin plus cephalexin. For those patients who have an allergy to penicillin, moxifloxacin or combination therapy with ciprofloxacin and clindamycin are appropriate choices. Azithromycin may also be effective for the penicillin-allergic patient, but it has less activity against anaerobes. Coverage for community-acquired MRSA (CA-MRSA) infection is not recommended because oral colonization of the human and animal mouth with CA-MRSA is unlikely. Cefazolin, an intravenous form of a first-generation cephalosporin, is not an appropriate treatment for this wound as Pasteurella species are resistant, just as they are to cephalexin, the oral form.

Answer 32

The correct response is Option E. The Centers for Disease Control and Prevention support criteria indicate that toxic shock syndrome may be diagnosed when patients present with a temperature exceeding 102°F (38.9°C), multisystems organ failure, rash, and/or multiple constitution symptoms. Exotoxin1 and exfoliative toxin-producing Staphylococcus aureus are the most common pathogen, but enterotoxin A, B, and C, producing Streptococcus pyogenes infections, yield a worse prognosis. Blood cultures may be negative for the causitive organism. Although Clostridium, Enterobactor, Pseudomonas, and Bacteroides species are polymicrobial species associated with necrotozing fasciitis, the description of this otherwise healthy patient is not consistent with its typical presentation of discolored blistered skin and crepitus.

Answer 33

The correct response is Option E. Bite injuries resulting from fistfights usually occur over the dorsal aspect of the third, fourth, or fifth metacarpophalangeal joint where a tooth penetrates the skin, extensor tendon, potentially the joint capsule, and even bone. When the hand is opened, the inoculating bacteria are dragged proximally by the extensor tendon and soft tissue. The patient may present acutely before clinical signs of an infectionCwith what appears to be a simple laceration or abrasion over the metacarpophalangeal jointCbut more typically after signs of infection have developed. If there are no signs of infection, it is prudent to explore the wound to rule out injury to the extensor tendon, joint capsule, and cartilage. To do so, the hand must be examined through the entire range of motion, particularly with the fingers flexed as in a clenched fist position. If there is no injury to the deeper structures, the wound can be washed out and the skin left open to heal by second intention. The patient can then be discharged with prophylactic antibiotics to cover the most common bacteria isolated from human bite wounds, i.e., Staphylococcus aureus, followed by Streptococcus species, Corynebacterium species, and Eikenella corrodens. Follow-up within 24 to 48 hours is important in outpatient management of these injuries. If injury is noted to the tendon, joint capsule, or joint cartilage, then operative washout and admission for intravenous antibiotics is appropriate. When the patient presents with a well-developed infection, antibiotic therapy alone is insufficient. Careful exploration must be performed to rule out injury and infection to deeper structures, most importantly the joint. Unrecognized or untreated pyarthrosis can lead to joint destruction and osteomyelitis. Inadequate exploration in the emergency department is usually due to inadequate anesthesia. Formal washout and drainage is sometimes best performed in the operating room. Elevation and immobilization are important in the management of edema in patients with hand infections. In the clinical scenario presented, however, this alone would be insufficient treatment because surgical drainage of the joint is required.

Answer 34

The correct answer is option C. Herpetic whitlow is most commonly caused by herpes simplex virus type 1. Herpetic whitlow can be extremely painful. In contradistinction to a true felon, the pulp space with HSV infection remains soft. Frequently the diagnosis is made on clinical rounds, but confirmation can be obtained with a Tzanck smear (lesion scraping and staining with toluidine blue, which reveals multinucleated giant cells with ground glass chromatin appearance, which is specific for HSV). Incision and drainage is contraindicated as the process usually is self-limited and surgical treatment may cause a secondary bacterial infection. The most infectious time period of the disease process is the late phase (beginning with 12–14 days for pain, blistering and ulceration formation, followed by 7–10 days for symptoms to subside, followed by approximately 12 days of viral shedding).

Answer 35

The correct response is Option A. Medicinal leeches are still commonly used as an adjunct in the treatment of venous congestion. They secrete a powerful anticoagulant called hirudin that promotes bleeding in the congested tissues until venous outflow can be reestablished. Leeches are also known to harbor the gram-negative bacterium Aeromonas. Because leeches can be exposed to open wounds on the patient for several days during treatment, antibiotic prophylaxis against Aeromonas is recommended. Ciprofloxacin, tetracycline, trimethoprim-sulfamethoxazole (Bactrim), and third-generation cephalosporins have all been shown to be effective against Aeromonas. However, in the scenario above, all of these antibiotics have a contraindication except cefotaxime, a third-generation cephalosporin. Ciprofloxacin is contraindicated in children when a suitable alternative exists secondary to the risk of arthropathy and arthrotoxicity. Similarly, the use of tetracycline is relatively contraindicated in children owing to the potential for abnormalities with the teeth, including permanent staining and growth retardation. While Bactrim is often used in children to treat various infections, this child has an allergy to sulfa drugs and should not be given this antibiotic. Clindamycin does not provide effective antibiotic coverage against Aeromonas.

Answer 36

The correct response is Option B. Rice bodies are pathognomonic for tuberculosis. Ziehl-Neelsen staining confirms the presence of acid-fast bacilli. All Mycobacterium and Nocardia species are potentially acid-fast. Many of these organisms are fastidious, so false-negative results are common. Surgeons should obtain multiple tissue samples and alert the laboratory that a diagnosis of tuberculosis is suspected. M. tuberculosis is traditionally cultured in Löwenstein-Jensen culture medium under specific temperature conditions 37.0°C (98.6°F). Histologic examination of specimens shows a granulomatous inflammatory process with the central portion of the granulomas appearing caseated. If a mycobacterial infection is suspected, a Mantoux test should be performed. The test involves purified protein derivative injection into the dermis and evaluation of the cutaneous site after 48 to 72 hours. M. tuberculosis should be considered in all immunocompromised patients. The other organisms can all be seen in hand infections in immunocompromised patients but do not produce rice bodies.

Answer 37

The correct response is Option E. Hidradenitis suppurativa is an inflammatory disease of the apocrine glands and follicular epithelium, presenting most commonly as deep recurrent infections or chronic sinus tracts in hair-bearing regions of the skin. It is most commonly seen in the axillary region in young women, but the groin and perineum may also be affected. After the diagnosis has been confirmed, a short course of treatment with local drainage and suppressive antibiotics is appropriate. However, once the disease process is established, the only appropriate therapy is complete excision of the scarred area. The successful treatment of chronic hidradenitis with injection of botulinum toxin A has been reported. Sweat glands have a sympathetic innervation. Botulinum toxin works by blocking the release of acetylcholine from nerve endings, thus decreasing sweat production. However, this is expensive and represents a temporary treatment of a chronic problem. The mainstay of treatment for larger areas is complete excision of axillary skin followed by split-thickness skin grafting. Negative pressure dressings are helpful to stabilize the graft. Although numerous local fasciocutaneous pedicled and free flaps have been described, they increase the risk of donor site morbidity and are generally not necessary. Healing by secondary intention has also been described. However, it is preferable to undertake excision of one axilla at a time so the patient is not disabled in the perioperative period.

Answer 38

The correct response is Option D. The patient described has cervical necrotizing fasciitis (CNF) that likely extends into the mediastinum. Pharyngeal and tonsillar infections, along with dental abscesses, are the most common sources of infection. Diabetes and other immunocompromised states are frequent comorbidities in this disease. Early presentation may be clinically indistinguishable from a superficial soft-tissue infection and, therefore, requires a high index of suspicion. Skin necrosis is often a late finding, as the infection begins in the fascial and deep tissues of the neck. CT scan is usually obtained to define the extent of the disease and may or may not show gas within the soft tissues. Patients are treated with broad-spectrum antibiotics and aggressive surgical debridement. Mastoiditis is an infection of the mastoid air cells usually arising in the setting of untreated otitis media. Mastoiditis can spread to surrounding structures, including the brain. Meningitis is an infection of the meninges that is associated with neck pain as well as fever, headache, and photophobia. It does not present with unilateral neck erythema and swelling. Parotitis is an infection of the parotid gland that usually arises in the setting of an obstructed parotid duct and is a very rare but potential cause of CNF. Sinusitis is not usually associated with CNF but may spread to the orbit, resulting in orbital cellulitis or orbital abscess, and, occasionally, cavernous sinus thrombosis. Cavernous sinus thrombosis is a life-threatening condition.

Answer 39

The correct response is Option D. This patient has a collar button abscess, which communicates from the volar web space to the dorsal aspect of the hand via the palmar fascia or lumbrical canal. Finger abduction is a characteristic finding. Appropriate management is drainage of the abscess using a combined volar and dorsal approach. The extensor tendons do not lie within sheaths on the dorsal aspect of the hand. Infection of the flexor tendon sheath is known as flexor tenosynovitis. This condition is diagnosed by the presence of one or more of Kanavel’s signs, including fusiform swelling, partial flexed posturing of the finger, tenderness over the flexor tendon sheath, and pain with passive extension of the finger. Finger abduction is not associated. Patients with infection of the palmar bursa have a painful prominence in the palm without finger abduction. Parona’s space lies between the pronator quadratus and flexor digitorum profundus tendons. It communicates with the flexor tendon sheaths to the thumb and small finger (radial and ulnar palmar bursa) and the midpalmar space. Infection within this space is characterized by painful swelling over the volar aspect of the wrist that occurs proximal to the flexion crease of the distal wrist.

Answer 40

The correct response is Option C. Purpura fulminans is a frequently fatal, rapidly evolving syndrome of septic shock and hemorrhagic bullae, which can result in massive desquamation. Management includes prompt recognition of the infection (which is usually caused by Neisseria meningitidis), initiation of broad €‘spectrum antibiotic therapy, mechanical ventilation, and aggressive fluid resuscitation with inotropic support. Disseminated intravascular coagulopathy (DIC) develops, and patients seem to benefit from replacement of activated protein C. A recently published multicenter, retrospective review of 70 patients documented an amputation rate of 90% and suggested the need for early fasciotomy to improve limb salvage. It is difficult to determine tissue viability during the resuscitation period; therefore, debridement, coverage, and amputation are delayed until demarcation has occurred.

Answer 41

The correct response is Option D. The most likely diagnosis is Fournier disease. Diabetes mellitus, alcoholism, heavy smoking, leukemia, and AIDS can predispose to this condition. Common sources of infection include urogenital disease, trauma, or recent manipulation (iatrogenic trauma, ie, endoscopic procedures). Key steps in treatment include early diagnosis, intravenous hydration, and broad-spectrum antibiotics (anaerobic coverage for Clostridium perfringens should continue as it is difficult to culture this). Immediate surgical debridement along fascial plains is of utmost importance. Orchiectomy is rarely needed, as testicles have their own blood supply and are protected by external spermatic fascia. Mortality rate is quoted to be 7% to 75%, with the higher rate in patients with diabetes, alcoholism, and in cases of delayed diagnosis.

Answer 42

The correct response is Option C. The most appropriate option for this patient is to proceed to the operating room for decompression/drainage of the flexor tendon sheath. This patient has all four of Kanavel’s signs, specifically pain on passive extension, fusiform swelling, flexor tendon sheath tenderness, and flexion of the affected digit. These point towards a diagnosis of flexor tenosynovitis, with the cause being the cat bite she sustained several days prior. Although cat bites only reflect 5% of all animal bites, they represent 76% of all infected bites, thought to be because of the morphology of their long teeth, which simulate a deep puncture wound. Outcomes studies demonstrate that because of this patient’s diabetes, she is at risk for a poor outcome, specifically the need for amputation and/or decreased total active motion. Other risk factors that can lead to these outcomes include age greater than 43 years, presence of subcutaneous purulence, digital ischemia, and polymicrobial infection. Given that she is at risk and that she has all four Kanavel’s signs, any intervention that is more conservative than operative decompression and drainage may lead to suboptimal outcomes. Administration of antibiotics (orally or intravenously) is not a substitute for drainage of the flexor sheath, especially in a case that presents more than 48 hours out from initiation of symptoms. Drainage in the emergency department is not as optimal as in the operating room given that the infection may limit efficacy of local anesthesia as well as the need for possible conversion to an open drainage procedure if closed catheter irrigation is insufficient.

Answer 43

The correct response for Item 198 is Option B and for Item 199 is Option E. Septic arthritis may result from extension of an adjacent subcutaneous abscess or by intra-articular contamination caused by a laceration or puncture wound. The joint is a poorly vascularized potential space, favoring colonization. Early diagnosis and drainage are crucial to treatment, as a joint infection can progress rapidly to destruction of articular cartilage. The two most common organisms that cause hand infections are Staphylococcus aureus and B €‘hemolytic streptococci. Minor staphylococcal and streptococcal infections are treated with first-generation cephalosporins. More significant infections of the interphalangeal joint should be performed through a midaxial incision. Neisseria gonorrhoeae usually manifests as a primary venereal infection. However, it can disseminate and sometimes present as a secondary hand infection, which is often confused with a purulent tenosynovitis or arthritis. It is important to distinguish gonococcal from pyogenic infection because, unlike a pyogenic infection, a gonococcal infection does not usually destroy tendon or articular cartilage. Therefore, incision, drainage, and debridement are unnecessary and should be avoided. Disseminated gonococcal infection is the most common cause of acute infectious arthritis in sexually active adults. A history or evidence of trauma are lacking. Fluid aspiration with Gram staining for gram €‘negative diplococci allows definitive diagnosis. Hospitalization and intravenous administration of a third €‘generation cephalosporin is recommended. Manifestations of Sweet syndrome can masquerade as acute hand infections. Sweet syndrome, originally described as an acute febrile neutrophilic dermatosis, belongs to a class of skin lesions that histologically have intense epidermal and/or dermal inflammatory infiltrate of neutrophils without evidence of infection or vasculitis. The lesions can erupt at sites of minor trauma. The clinical picture is consistent with infection initially. The unresponsiveness of these lesions to antimicrobial therapy and the lack of associated cellulitis is a clue to the diagnosis. The treatment of choice involves a tapering dose of corticosteroids. Herpetic whitlows are often confused with paronychia or felon and are treated mistakenly as such. Initial signs include intense pain and erythema of the fingertip, followed by edema and tenderness. A Tzanck smear of vesicular fluid may show multinucleated giant cells. Primary herpes simplex infections typically resolve without treatment within three weeks. Incision and drainage of herpetic whitlow is contraindicated because surgical treatment converts a closed wound to open and may result in a secondary bacterial infection or viral superinfection. To date, there have been no controlled studies that assess the efficacy of acyclovir for the treatment of herpetic whitlow, b

Answer 44

The correct answer is option C. Fungal infections of the upper extremity are of four main types—cutaneous, subcutaneous, deep, and systemic. Cutaneous infections are caused by organisms capable of metabolizing keratin. The suspected organism in this case is Sporothrix schenckii. A thorn puncture is the usual mechanism of joint inoculation. Arthrotomy with synovectomy, appropriate cultures, and antifungal medication would be the best treatment. Itraconazole (100mg–200mg daily) is the preferred medication. The organism grows best at temperatures below 37°C; ice application would therefore be contraindicated. Steroid injection could potentially accelerate the infectious process. Physical therapy would not address the infection. Cephalosporins would not be effective against a fungal infection, which would be suggested by the more subacute course of this patient.

Answer 45

The correct response is Option A. Because scorpion stings are typically self-limiting in adults, management should be limited to observation and application of cold compresses. Six closely related species of scorpion found in the southwestern United States cause medically significant injuries resulting from a sting. These species are typically 1 to 7 cm long and yellow-brown in color, possibly with vertical bands. The venom is neurotoxic, resulting in activation of the autonomic nervous system and depolarization of the neuromuscular junctions. Affected patients have intense localized pain and hyperesthesia; there is severe pain with light tapping over the area of the wound. Other symptoms seen in patients who sustain scorpion stings include blurred or diminished vision, strabismus, dyspnea, wheezing, dysphagia, urinary or fecal incontinence, opisthotonos, fever, and involuntary muscle contractions. Hospital admission is recommended for children who have scorpion stings because envenomation is much more dangerous than in adults. Appropriate pediatric management includes airway control, sedation, cardiac monitoring for potential arrhythmias, and administration of calcium gluconate for treatment of muscle spasms. Narcotic agents should not be administered as they may exacerbate the neurotoxic effects. Scorpion antivenin is available for use in Arizona. The use of tourniquets is not recommended in patients with scorpion stings. Debridement is not necessary because scorpion venom has only localized adverse effects on soft tissue.

Answer 46

The correct response is Option E. This 34-year-old man has findings consistent with advanced flexor tenosynovitis. The diagnosis can be made by the presence of one or more of Kanavel’s four signs (fusiform swelling, partial flexed posturing of the finger, tenderness over the flexor tendon sheath, and pain with passive extension of the finger). This patient exhibits three of the diagnostic signs, indicating an advanced disease course. In addition to intravenous administration of antibiotics, the most appropriate management is opening and irrigation of the flexor tendon sheath. The surgeon should make an incision into the palm that is sufficiently wide to allow for access to and visualization of the proximal aspect of the A1 pulley. Another incision is made distally to allow access to the A4 and A5 pulleys. If necessary, the incisions can be extended distally and/or proximally to treat infected, necrotic tissue. In patients with advanced flexor tenosynovitis, the flexor digital sheath is typically distended with purulent material. A plastic irrigation catheter is inserted at the level of the A1 pulley and threaded distally into the sheath to allow for irrigation beyond the A5 pulley. This technique will facilitate complete decompression of the sheath without sacrificing the pulleys. Irrigation can be provided via the catheter continuously for as long as 24 hours, depending on the severity of infection. Needle aspiration is useful in establishing a diagnosis of or treating early tenosynovitis (characterized by the presence of only one or two of Kanavel’s signs) or as initial treatment during pregnancy. Simple incision into the finger, joint, or palm will not address in the infection of the flexor tendon sheath.

Answer 47

The correct response is Option B. Necrotizing soft-tissue infections are rapidly progressive, polymicrobial infections that require prompt diagnosis, debridement of devitalized tissue, and administration of appropriate antibiotics. Some studies have shown that mortality rates in necrotizing infections can be reduced with the addition of hyperbaric oxygen treatment. High-dose corticosteroids, intravenous gamma globulin, and topical papain-urea ointment have not been shown to increase survival rates of necrotizing soft-tissue infections.

Answer 48

The correct response is Option C. The currently accepted decolonization protocol from the Infectious Diseases Society of America is a combination of topical nasal mupirocin ointment and a chlorhexidine body wash for 5 days. The most robust data for decolonization are in the cardiac surgery literature; the Society of Thoracic Surgeons guidelines recommend routine prophylaxis for all patients undergoing cardiac surgery. These guidelines are based on studies that show a decreased rate of sternal wound infections. The carriage rate of methicillin-resistant Staphylococcus aureus for health care workers is approximately 5% based on large review studies. As a substantial portion of cases originate from nasal colonization, routine screening and decolonization are recommended in areas where the carriage rate exceeds 10% (Centers for Disease Control and Prevention recommendation). The other antibiotics listed are reserved for the treatment of infection rather than as part of a decontamination protocol.

Answer 49

The correct response is Option E. This 48-year-old nurse has findings consistent with streptococcal toxic shock syndrome caused by invasive infection with Streptococcus organisms. This condition is characterized by pain disproportionate to the level of injury. Affected patients typically have other minor symptoms, in addition to pain, and have been known to seek treatment frequently before the correct diagnosis is established. Streptococcal toxic shock syndrome is confirmed by the presence of coagulation difficulties and hepatic and renal abnormalities. Clostridial necrotizing fasciitis has symptoms similar to streptococcal toxic shock syndrome but is differentiated by subcutaneous emphysema and air in the tissues on radiographs. With anthrax contamination, primary routes of inoculation are cutaneous and inhalational. Cutaneous anthrax is characterized by a single lesion that initially resembles an insect bite but then becomes ulcerated. Skin trauma is not associated. Pseudomonas ecthyma gangrenosum is an infection that demonstrates rapid progression and is frequently fatal. It occurs in patients with febrile neutropenia, and is often a complication of chemotherapy administered for lymphoreticular malignancies. Although staphylococcal cellulitis is not associated with systemic manifestations, patients with staphylococcal toxic shock syndrome can have failure of multiple organ systems.

Answer 50

The correct answer is option E. Septic arthritis may result from extension of an adjacent subcutaneous abscess or by intra-articular contamination caused by a laceration or puncture wound. The joint is a poorly vascularized potential space, favoring colonization. Early diagnosis and drainage are crucial to treatment, as a joint infection can progress rapidly to destruction of articular cartilage. The two most common organisms that cause hand infections are Staphylococcus aureus and B-hemolytic streptococci. Minor staphylococcal and streptococcal infections are treated with first-generation cephalosporins. More significant infections of the interphalangeal joint should be performed through a midaxial incision. Neisseria gonorrhoeae usually manifests as a primary venereal infection. However, it can disseminate and sometimes present as a secondary hand infection, which is often confused with a purulent tenosynovitis or arthritis. It is important to distinguish gonococcal from pyogenic infection because, unlike a pyogenic infection, a gonococcal infection does not usually destroy tendon or articular cartilage. Therefore, incision, drainage, and debridement are unnecessary and should be avoided. Disseminated gonococcal infection is the most common cause of acute infectious arthritis in sexually active adults. A history or evidence of trauma are lacking. Fluid aspiration with Gram staining for gram-negative diplococci allows definitive diagnosis. Hospitalization and intravenous administration of a third-generation cephalosporin is recommended. Manifestations of Sweet syndrome can masquerade as acute hand infections. Sweet syndrome, originally described as an acute febrile neutrophilic dermatosis, belongs to a class of skin lesions that histologically have intense epidermal and/or dermal inflammatory infiltrate of neutrophils without evidence of infection or vasculitis. The lesions can erupt at sites of minor trauma. The clinical picture is consistent with infection initially. The unresponsiveness of these lesions to antimicrobial therapy and the lack of associated cellulitis is a clue to the diagnosis. The treatment of choice involves a tapering dose of corticosteroids. Herpetic whitlows are often confused with paronychia or felon and are treated mistakenly as such. Initial signs include intense pain and erythema of the fingertip, followed by edema and tenderness. A Tzanck smear of vesicular fluid may show multinucleated giant cells. Primary herpes simplex infections typically resolve without treatment within three weeks. Incision and drainage of herpetic whitlow is contraindicated because surgical treatment converts a closed wound to open and may result in a secondary bacterial infection or viral superinfection. To date, there have been no controlled studies that assess the efficacy of acyclovir for the treatment of herpetic whitlow, but case reports suggest that it both suppresses and decreases the length and severity of recurrent infections when taken orally.

Answer 51

The correct response is Option B. Bacterial resistance to host defense peptides is an unfortunate reality that is clinically and experimentally observed. The significant diversity of host defense peptide mechanisms requires the resistance strategies to use equally numerous solutions based on the specific peptide or target organism. Common resistance mechanisms used by bacteria against host defense peptides include: 1) decreased carotenoid content in cell membranes (not increased) 2) increased protease expression (not inhibition) 3) biofilm production (not reduction) 4) increased expression of binding ligands to host defense peptides (not suppression) Esterification of cell membrane lipoteichoic acid with D-alanine is a commonly used mechanism of gram-positive bacterial antimicrobial resistance. REFERENCES: 1. DeLong MR, Tandon VJ, Da Lio AL, Deming TJ, Cederna PS. Overview of host defense peptides and their applications for plastic and reconstructive surgeons. Plast Reconstr Surg. 2020;146(1):91-103. doi:10.1097/PRS.0000000000006910 2. Kraus D, Peschel A. Molecular mechanisms of bacterial resistance to antimicrobial peptides. Curr Top Microbiol Immuno. 2006;306:231-235. doi: 10.1007/3-540-29916-5_9

Answer 52

The correct response is Option C. This patient has chronic paronychia, which is a recurrent abscess beneath the eponychial edge of the fingernail associated with repeated exposure to a moist environment. In patients with this condition, Candida albicans is the most frequently cultured organism. Chronic paronychia can evolve following an acute episode if drainage of the abscess is inadequate or inappropriate antimicrobial agents are prescribed. Removal of a segment of nail plate is indicated in patients with acute paronychia if there is drainage beneath the plate. In a patient who has paronychia that appears to be caused by a fungal organism, management should focus on administering oral and topical antifungal agents, such as itraconazole and ketoconazole, and minimizing the moist environmental conditions that have predisposed the patient to the infection. If the infection does not respond to treatment, radiographs should be obtained to determine bony involvement. In addition, biopsy specimens and cultures of soft tissue and/or bone may be indicated to identify the pathology of the condition, as the underlying cause may be a misdiagnosed malignant tumor. If radiographs, biopsy specimens, and cultures show no disease, appropriate management is excision of the thickened dorsal nail roof (ie, marsupialization), typically a crescent-shaped piece with a width of 3 to 5 mm. Simple repeat incision and drainage alone will not prevent recurrence. Obliteration of the nail matrix or amputation of the fingertip will not address the symptoms.

Answer 53

The correct response is Option A. In this patient who has a history of recurrent inflammation consistent with chronic paronychial infection, the most likely causal organism is Candida albicans, which has been shown to be responsible for as many as 97% of cases of chronic paronychia. In patients with this condition, the affected area should be kept dry and a topical antifungal agent such as clotrimazole should be applied. Eponychial marsupialization, which involves the removal of a crescent-shaped piece of skin from the eponychium, may be considered to clear the scarred, infected tissues. Herpes simplex virus results in herpetic whitlow, an extremely painful condition characterized by visible vesicles. It is self-limiting and typically resolves in three to four weeks, but may recur. Incision and drainage are not indicated. Mycobacterium marinum, an atypical mycobacterium, can result in superficial or deep granulomatous infections. The recommended treatment includes multidrug antituberculous therapy and surgical debulking. Although Pseudomonas aeruginosa is part of the normal flora of the hyponychial space, this organism can result in acute infection in patients with diabetes mellitus or can be a secondary cause of chronic paronychia. Discoloration of the nail is a frequent finding. Staphylococcus aureus is the predominant pathogen associated with acute paronychial infection, which manifests as an abscess requiring incision and drainage.

Answer 54

The correct answer is option a. The thenar space extends from the third metacarpal to the thumb. It is contiguous with and separated from the midpalmar space by the midpalmar oblique septum. A collar-button abscess in the second web space will, like flexor tenosynovitis of the index finger, drain into the thenar space. Flexor tenosynovitis of the long and ring fingers and third web space infections will drain into the midpalmar space. Finally, small finger flexor tenosynovitis will track through the ulnar bursa and not the midpalmar space. The dorsal subaponeurotic space is just deep to the extensor tendons of the hand and does not communicate with the thenar or midpalmar spaces. Parona’s space is in the forearm between the superficial and deep flexor compartments. The natatory space is not a named space.

Answer 55

The correct answer is C. The patient is diagnosed with necrotizing fasciitis (type 2, monomicrobial), caused by Group A Streptococcus pyogenes. While this condition is rare following aesthetic surgery, most reported cases are associated with liposuction, and S. pyogenes is the predominant organism involved. The cornerstone of treatment includes surgical debridement and targeted antibiotic therapy with clindamycin and penicillin. Clindamycin is effective in inhibiting streptococcal toxin and cytokine production; however, it is not recommended as monotherapy initially due to the risk of clindamycin resistance. Therefore, it should be used in combination with penicillin until antimicrobial susceptibility testing guides de-escalation of therapy. Other less common type 2 infections caused by a single microorganism include methicillin-resistant Staphylococcus aureus (MRSA), Aeromonas hydrophilia, and Vibrio vulnificus. Type 1 necrotizing fasciitis is typically polymicrobial and may involve both aerobic and anaerobic bacteria. The presence of gas gangrene in type 1 infections often suggests clostridial species. Initial treatment for type 1 infections typically involves a combination of vancomycin or linezolid with piperacillin-tazobactam, a carbapenem, ceftriaxone, metronidazole, or a fluoroquinolone with metronidazole. Therapy should then be adjusted according to culture sensitivities. Vancomycin monotherapy is not recommended as an initial treatment for either type 1 or type 2 necrotizing fasciitis. 1. Marchesi, A., Marcelli, S., Parodi, P. C., Perrotta, R. E., Riccio, M., & Vaienti, L. (2017). Necrotizing fasciitis in aesthetic surgery: A review of the literature. Aesthetic Plastic Surgery, 41(2), 352-358. https://doi.org/10.1007/s00266-016-0754-2 2. Stevens, D. L., & Bryant, A. E. (2017). Necrotizing soft-tissue infections. New England Journal of Medicine, 377(23), 2253-2265. https://doi.org/10.1056/NEJMra1600673 3. Stevens, D. L., Bisno, A. L., Chambers, H. F., et al. (2014). Practice guidelines for the diagnosis and management of skin and soft tissue infections: 2014 update by the Infectious Diseases Society of America. Clinical Infectious Diseases.

Answer 56

The correct response is Option D. The brown recluse spider (Loxosceles reclusa) is one of two species of North American spider capable of envenomation. It is generally found throughout the southern United States. This spider is believed to be nocturnal but may also be active during the day; it does not weave a web. Features include long slender legs and a distinctive fiddle-shaped marking on its dorsal cephalothorax. Both male and female brown recluse spiders are venomous. Most patients are unaware that they have been bitten by this spider until pain develops or the wound becomes noticeable. Blistering, ischemia, and ulceration may be seen and can ultimately lead to necrosis. Conservative treatment with administration of dapsone 100 mg daily for 14 days is advocated as the injury is often more extensive than initially thought. There is no antivenin to brown recluse spider venom. Dapsone is a leukocyte inhibitor that has both bacteriostatic and bacteriocidal properties and is frequently used in the treatment of leprosy. Hemolysis is the most common adverse effect of dapsone therapy. Because of the risk for hemolysis and other hematologic side effects, including methemoglobinemia, blood counts should be measured weekly. In addition, dapsone should not be administered to patients who have glucose-6 phosphate dehydrogenase deficiency. Diarrhea, diplopia, headache, and peripheral neuropathy are not complications of dapsone therapy.

Answer 57

The correct response is Option A. Apocrine glands are associated with sweat production and when mixed with bacteria produce body odor, which can be malodorous. There are two types of sweat glands, eccrine and apocrine. Eccrine glands are located throughout the body and secrete primarily water and salt. Apocrine glands are located in hair-bearing areas such as the axilla and groin and secrete watery fluid that is higher in protein. There are three types of exocrine secretion. Merocrine glands secrete via exocytosis and no part of the glands is damaged or lost. Eccrine glands are a type of merocrine gland. Apocrine glands secrete via membrane budding and loss of cytoplasm. The mammary glands are a type of apocrine gland. Finally, holocrine glands secrete via membrane rupture, which destroys the cell. Examples include sebaceous glands, which contain remnants of dead cells, as well as meibomian glands of the eyelids. Hyperhidrosis describes excessive sweating through the eccrine glands where there is an increase in number and size of these glands. Osmidrosis, or bromhidrosis, involves excess secretion of the apocrine glands combined with bacterial proliferation with corynebacterium. Enzymatic breakdown of the glandular secretions results in the malodor.

Answer 58

The correct response is Option A. This patient has compartment syndrome due to a snake bite. Pain is the hallmark of compartment syndrome and is accentuated by passive stretching of the involved muscle compartment, which is the most consistent early sign. Patients with injuries of the upper and lower extremities should be closely monitored for the presence of muscle, nerve, and tissue ischemia. However, compartment syndrome occurring in conjunction with a pit viper or other snake bite is often worse than other types of compartment syndrome. Because the venom is injected directly into the tissues, tissue destruction occurs rapidly, leading to the immediate onset of edema, ecchymosis, and swelling. Measurement of compartment pressures is an important step in the diagnosis of compartment syndrome, especially in patients who have sustained head trauma or spinal cord injuries. Decompressive fasciotomy should be performed in normotensive patients when compartment pressures are greater than 30 mmHg and the duration of symptoms is longer than eight hours or is unknown or the patient is unconscious or uncooperative. Patients with hypotension and compartment pressures greater than 20 mmHg should also undergo surgery within six hours. In some patients with compartment syndrome, central or peripheral sensory deficits or late nerve ischemia may preclude the presence of pain as a diagnostic finding. In compartment syndrome, distal pulses may still be present. The affected extremity may appear cyanotic, pale, or normal. Sensation may be normal or diminished. Tenseness and tenderness of the closed compartments are nonspecific findings that are not necessarily associated with ischemic tissue damage.

Answer 59

The correct response is Option B. Eikenella corrodens is an anaerobic organism present in human oral flora and has been associated with human bite wounds. Group A Streptococcus is also a common pathogen in a fight bite injury like the one this patient has. This patient has most likely sustained a “fight bite,” which results from tooth penetration of the metacarpophalangeal (MCP) joint after striking someone in the mouth with a clenched fist. These injuries can often be underappreciated, as the underlying defect in the extensor hood and joint capsule may not be seen on examination when the fingers are extended during examination in an emergency department. The joint can become contaminated with oral flora. Penetrating injury with high bacterial load can result in a septic joint and lead to destruction of cartilage and osteomyelitis. Recreation of the flexed fist position may help in lining up the structures and assist in identification of the injury. Treatment is aggressive antibiotic therapy and surgical exploration with irrigation and debridement of the joint to remove debris. Clostridium perfringens is a gram-negative rod associated with gas gangrene, which results in subcutaneous crepitus and can be rapidly progressive. Pasteurella multocida is a gram-negative anaerobic bacterium most commonly associated with cat bite infections. Pseudomonas aeruginosa is a gram-negative rod that can be associated with diabetic wound infections. And Staphylococcus epidermidis is a gram-positive cocci present on the skin. It has been associated with implant infections. None of these pathogens are as likely to be present in a fight bite as Eikenella corrodens.

Answer 60

The correct response is Option B. Hidradenitis suppurativa (HS), also known as acne inversa, is a chronic inflammatory disease of the skin and subcutaneous structures. Initially presenting as tender, subcutaneous nodules, the disease can advance to cause abscesses and large areas of subcutaneous scarring and draining sinus tracts. Historically, HS has been thought to originate from the apocrine sweat glands. However, research in recent years has demonstrated that the mechanism is one of follicular occlusion: hair follicles become occluded due to an overproliferation of ductal keratinocytes, rupture, and subsequently re-epithelialize. As this cycle continues, sinus tracts form that house bacteria and cause chronic, painful infections and inflammation that can involve the skin and subcutaneous structures including muscle, fascia, and lymph nodes. HS lesions typically occur predominately in the apocrine-gland bearing areas of the axillary, inguinal, perianal, and perineal areas. Lesions typically correspond with the “milk-line” pattern of apocrine-related mammary tissue in mammals. Eccrine, or merocrine, sweat glands are found throughout the body, but their highest concentrations are in the palms and soles. These areas are typically spared by HS. Follicular pyodermas, including folliculitis, furuncles, and carbuncles, arise primarily from the infection of hair follicles. They do not cause the sinus tracts, comedones, and scarring caused by HS. Granuloma inguinale is a sexually transmitted infection of the genitalia, perineum, and/or perineal area caused by Klebsiella granulomatis. Pyoderma gangrenosum is a dermatologic condition mediated by neutrophils that causes skin ulceration and breakdown.

Answer 61

The correct response is Option B. The most appropriate next step in management is to initiate intravenous dexrazoxane. Recent data support the use of this agent in extravasation of anthracyclines (e.g., doxorubicin) as an antidote. It has been shown to decrease the frequency and severity of tissue injury. The mechanism by which dexrazoxane diminishes tissue damage is unknown. However, two mechanisms of action are hypothesized: 1) reduction of oxidative stress due to complexes of metal ions and anthracyclines by chelating metal ions; 2) and blockade of topoisomerase II poisons by catalytic inhibition of topoisomerase II. Patients receive treatment with dexrazoxane 1000 mg/m2 administered intravenously on days 1 and 2, and 500 mg/m2 on day 3. The infusion is given in the opposite arm of the extravasation site and is administered as soon as possible and no longer than 6 hours after the extravasation accident. Flushing the port is not indicated because the port may be malfunctioning and this action could extravasate the flushing agent. Adding more fluid to the area (extravasation of saline from the port, subcutaneous saline injection, etc.) will only add to the pressure on the overlying skin, injuring the skin further. Removal of the port is not indicated until it has been ascertained it is malfunctioning. Dimethyl sulfoxide (DMSO) is a known treatment option for anthracycline extravasations. However, it is used as a topical agent with or without cortisone, not as a subcutaneous injection. Additionally, it should not be used in patients who are receiving dexrazoxane because it has been shown to decrease the efficacy of the dexrazoxane therapy.

Answer 62

The correct response is Option D. Tenosynovitis is a bacterial infection within the sheath of the extrinsic flexor tendons of the hand. Suppurative infection of the sheath can develop over time. Classic signs of tenosynovitis include fusiform swelling, partial flexed posturing of the digit, and tenderness along the flexor tendon sheath; however, other inflammatory processes can cause these findings. In contrast, the fourth classic sign, pain with passive extension of the digit, is the most sensitive test for flexor tenosynovitis. Aspiration of the affected tendon sheath will yield purulent drainage. Diagnosis can be confirmed with Gram's stain. In patients with established tenosynovitis, the most appropriate management is surgical irrigation and/or drainage of the tendon sheath. This is best accomplished with a proximal incision at the level of the A1 pulley and a distal incision at the distal flexor crease; the fibroosseous canal is then irrigated copiously. In patients with more extensive infection, open drainage and debridement may be required. Drainage from a finger wound is more likely to be caused by local wound infection than by tenosynovitis.

Answer 63

The correct response is Option B. The most appropriate first step in management in the scenario described is to aspirate fluid from the joint for analysis. There are several conditions that mimic acute hand infections, and it is important to recognize them so that the appropriate treatment can be initiated. Crystalline deposition diseases, such as gout and pseudogout, tend to present with joint swelling, erythema, pain with motion, and fever, much like the signs of infection. The only way to confirm the diagnosis is to aspirate the joint and look for crystals with polarizing microscopy. Though the description of the thumb in the scenario described is consistent with possible infection, the fact that there has been no trauma or break in the skin around the joint, and the patient’s history of acute arthritic episodes in other joints, raises some suspicions that this could be noninfectious. Therefore, joint aspiration to rule out other causes of acute arthritis is warranted. Administration of antibiotics and elevation and splinting should begin after the aspiration, if indicated. MRI of the joint and surgical washout are not indicated at this time.

Answer 64

The correct response is Option D. The most appropriate next step in management is to surgically explore the wound in the operating room. The clinical picture is of a severe, rapidly progressing infection, possibly necrotizing fasciitis. A high index of suspicion and early treatment are vital for successful outcomes. Necrotizing fasciitis is a rare and rapidly progressive infection of the deeper layers of skin and subcutaneous tissues, easily spreading across the superficial fascial plane, with subsequent death of the overlying skin and severe systemic toxicity. Liposuction is the most frequently associated cosmetic surgery with this infection. Signs and symptoms are insidious, nonspecific, or virtually unnoticeable early in the course of the disease. Later, erythema, prominent edema, and induration appear, accompanied by intense or intolerable pain. The clinical picture evolves into systemic toxicity and eventually multiple organ failure. Risk factors for necrotizing fasciitis include diabetes mellitus, immunosuppression, age older than 50 years, malnutrition, and peripheral vascular disease. There are two forms of the disease: one caused by Streptococcus pyogenes, and the other by mixed infections caused by a variety of microbes, including Escherichia coli, Proteus, Serratia, and Staphylococcus aureus. The progressive necrosis of the tissues typically involves the superficial fascia and the subcutaneous layer. The extent of the gangrene at the fascial layer is typically more severe and greater than at the skin level. This insidious infection is virtually unnoticeable and nonspecific in the first 24 to 48 hours; however, in the following days, an extensive, hardened area appears, which is often dark colored in the center. Intense pain and skin necrosis follow at the level of the infection. Metabolic changes occur, ending with respiratory distress, oliguria, acidosis, increased creatine kinase activity, increased troponin concentrations, and toxic syndrome. Diagnosis and treatment consists of surgical exploration and debridement that reveal necrotic, edematous subcutaneous fat. Bacteriologic analysis of exudate, cultures, and histologic evaluation complete the diagnosis. Early diagnosis is imperative to avoid a fatal outcome. Because necrotizing fasciitis is a progressive, rapid infection, a staged “second-look” operation and, if necessary, additional debridement should be performed. The mortality rates are high and range from 20 to 70%, but decrease to 4.2% after immediate surgical intervention. Though antibiotic therapy is an integral part of the treatment, surgical exploration is key. CT scans and ultrasonography will not change the treatment plan and are therefore not the appropriate next step in management.

Answer 65

The correct response is Option B. Necrotizing fasciitis is a severe form of subcutaneous infection that tracks along fascial planes often extending beyond the superficial signs of infections. Early diagnosis and treatment are critical in reducing mortality. Early surgical intervention is often required for diagnosis and treatment. Initial antibiotic therapy is directed at the most likely pathogens. Two clinical subtypes of necrotizing fasciitis have been identified. Type I is a polymicrobial infection caused by aerobic and anaerobic bacteria occurring primarily in patients who are immunocompromised or have certain chronic diseases like diabetes. Type II is a monomicrobial infection that can occur in healthy individuals in any age group. Often, the individual has a history of blunt trauma, penetrating injuries or lacerations (often minor), surgical procedures, childbirth, or burns. In Type II fasciitis, the most common causative organisms are group A streptococci. Clindamycin and penicillin in combination are recommended. Clindamycin has been shown to suppress toxin production, whereas metronidazole has not. Clindamycin also facilitates phagocytosis of Streptococcus pyogenes. Penicillin is added because of increasing resistance of group A streptococci to clindamycin. Infection with Staphylococcus aureus is a less common cause of Type II necrotizing fasciitis. Oxacillin could be used to treat susceptible S. aureus infection, whereas vancomycin is appropriate therapy for methicillin-resistant S. aureus (MRSA). Type I necrotizing fasciitis requires a multiple antibiotic regimen to cover aerobic and anaerobic bacteria. Therefore, broad €‘spectrum coverage with ampicillin €‘sulbactam, clindamycin, ciprofloxacin, or gentamicin is recommended.

Answer 66

The correct response is Option E. The infection described is most likely caused by a subset of Staphylococcus aureus, which is methicillin €‘resistant. Although methicillin €‘resistant S. aureus (MRSA) has traditionally been iatrogenic in its etiology, community €‘acquired MRSA is becoming more prevalent. In the Emergency Department population, the proportion of soft tissue infections presenting with MRSA is increasing. MRSA is not sensitive to penicillin €‘related antibiotics such as piperacillin/tazobactam and typically requires vancomycin or linezolid for effective treatment. Older antibiotics such as clindamycin and trimethoprim €‘sulfamethoxazole may also be effective in treating MRSA. MRSA takes longer than the other bacteria listed to grow out in culture. Bacteroides fragilis, Escherichia coli, group B streptococcus, and Pseudomonas aeruginosa are all common bacteria found in abscesses of the hand; however, they are all sensitive to penicillin €‘related antibiotics such as piperacillin/tazobactam.

Answer 67

The correct response is Option E. Although **tigecycline** has excellent coverage of most staphylococcal and many gram-negative rod infections, this tetracycline derivative is *not effective against pseudomonal infections*. Patients with pseudomonal sepsis benefit from double coverage. Furthermore, sensitivities to different antimicrobial agents are quite variable from one health care system to another, so providers must remain vigilant after beginning therapy and change coverage based on lack of clinical response and determination of final sensitivities. An essential component of this patient's care would be urgent burn wound excision, after he has been resuscitated and empiric antibiotics have been initiated.

Answer 68

The correct response is Option A. It is important to recognize dorsal hand lacerations as a possible site for serious infection, especially in the context of altercations where a "fight bite" might have occurred. In some cases, patients may be apprehensive to admit to the source of their injury, and in these cases, physicians should err on the side of caution and provide antibiotic prophylaxis. The primary bacteria isolated from human bite wounds is Eikenella. Pasteurella is commonly found in wounds resulting from the bites of dogs, cats, or farm animals. Flavobacterium is associated with bites from freshwater fish. Mycobacterium can be seen in bites from bears and ferrets. Vibrio is associated with shark bite wounds and other marine injuries.

Answer 69

The correct response is Option E. The most likely diagnosis is tenosynovitis, an infection involving the gliding surface of the flexor tendon sheath that typically develops following a puncture wound. Staphylococcus aureus is the most likely causative organism. The four essential signs of tenosynovitis are fusiform swelling, partial flexed posturing of the digit, tenderness along the flexor tendon sheath, and pain with passive extension of the digit. Cellulitis is a common superficial infection that typically affects the dorsal aspect of the hand and is characterized by erythema, edema, and lymphangitis. Beta-hemolytic streptococcus is most frequently associated. Felons are infections of the pulp space (which is compartmentalized by septa) typically caused by Staphylococcus aureus. Although tenosynovitis may develop in a patient with an advanced felon, the infection is more likely to be localized at the pulp initially, and the patient would have throbbing pain, especially when the finger is placed in a dependent position. Patients with osteomyelitis have localized pain, swelling, and erythema along the course of one of the long bones of the hand. This condition often develops secondary to localized infection by hematogenous spread. In patients with paronychia, the structures surrounding the proximal and lateral nail become infected. This condition is characterized by pain, especially in the region of the nail fold, and erythema. Staphylococcus aureus is the most frequently identified cause of acute paronychia, and Candida albicans is most likely to cause chronic paronychia.

Answer 70

The correct response is Option E. Analysis of synovial fluid is the most useful diagnostic test. The most definitive test of the joint fluid, bacterial Gram stain and culture, is unfortunately not consistently positive in an acute septic joint. Culture may be negative in about 50% of cases, especially gonococcal, and Gram stain is even less frequently positive. One has to wait a few days for culture results. As one lowers the threshold for the white cell count in a joint aspirate, the test becomes more sensitive, but less specific. If the white cell count threshold is set at 50,000/mL, which is traditionally the value considered to be the threshold for diagnosis of a septic joint, the sensitivity is 61%. If a white cell count at 17,500 is set as the threshold, the sensitivity is 83%, but specificity is 67%. The specificity rises to 77% if the threshold for the white cell count is raised to 100,000. Sedimentation rate, serum white cell count, and C-reactive protein do little to change pretest probability of a septic joint. Radiographic changes are a late finding in septic arthritis.

Answer 71

The correct answer is option a. This patient has developed an infection caused by a member of the poxvirus family that is endemic in sheep and goats. In humans the infection is known as human orf infection. An identical infection may occur from contact with infected cattle in which case it is known as milkers’ nodule. In either case the disease is self limiting and typically resolves within six weeks in immunocompetent hosts. Failure to recognize the correct diagnosis may lead to unnecessary surgical interventions including amputation.

Answer 72

The correct response is Option C. The patient described has a web space (collar-button) abscess. Pus resides dorsal to and volar to the natatory fibers of the palmar fascia with a small connection between the two spaces passing through the natatory fibers. It is drained through proximal dorsal and volar incisions in the web space. One should not incise through the apex of the web space, as this may lead to a web space contracture. Incisions are allowed to heal by secondary intention. Cleland ligament is a separate portion of the palmar fascia located within the finger dorsal to the neurovascular bundle. It is distal to the purulence in a web space abscess. Absence of pain with axial loading of the digits makes a joint space infection unlikely, so drainage of the metacarpophalangeal joint is unnecessary. Some approaches to drainage of flexor tenosynovitis involve release of the proximal sheath through the A1 pulley; the appearance in the photo (lack of fusiform swelling), and absence of pain with passive extension of the fingers, make flexor tenosynovitis unlikely in this patient. Infection of the mid-palmar space would produce more proximal pain and swelling in the palm, which is not present in this patient.

Answer 73

The correct response is Option E. A paronychia is an infection occurring in the space between the nail plate and the paronychial or eponychial fold. Common causes include nail biting and aggressive manicuring. In an otherwise healthy individual, Staphylococcus aureus and Streptococcus species are the most common pathogens causing a paronychia. The remaining bacteria listed would only be expected to cause a paronychia in special circumstances. Enterococcus is an enteric bacterium. Mycobacterium marinum can be present in aquatic environments including fish tanks and has also been reported in the Chesapeake Bay. Pasteurella multocida is a common flora of cat mouths. Pseudomonas occurs in areas with moist environments and can be problematic in a burn unit.

Answer 74

The correct response is Option E. Hidradenitis is a chronic and often disabling skin condition of the apocrine glands. It results in abscesses, inflammatory nodules, and draining sinuses in the axillae, groin, perineum, and occasionally the submammary area. It affects approximately 1 in 300 people, and it is more common in women, people who smoke, and people who are overweight. The axillae are more commonly involved in women, and the perineum more commonly in men. Early treatment centers around local wound care, oral antibiotics, corticosteroid injections, hygiene, weight loss, and smoking cessation. Decreased estrogen levels may also contribute, and disease often subsides with oral contraceptives and during pregnancy. Unresponsive or extensive disease requires surgical intervention for long-term resolution. Relapse rates are high, and healing is often slow. Although limited excision and closure of solitary lesions is an effective short-term treatment, new lesions are likely to develop. Fistulotomy alone has an unacceptably high recurrence rate. A long-term resolution in this severely affected patient requires complete excision of the hair-bearing skin of the affected area. The large defect created needs broad skin coverage. The best options include split-thickness skin grafting or grafting with negative pressure wound therapy immobilization. Negative pressure wound therapy followed by healing by secondary intention or coverage with local flaps are additional options, though scar contractures and shoulder stiffness are risks. Laser treatments are too superficial to treat the deeper apocrine structures. Lymphadenectomy is not necessary for a cure.

Answer 75

The correct response is Option B. The most appropriate next step in management is to update this patient €™s tetanus status and observe closely for signs and symptoms of envenomation. The area of involvement should be outlined with a marking pen and the patient observed closely for progression of local tissue injury, clinical evidence of coagulopathy, and hemodynamic instability. In the United States, 99% of snake bites are caused by the Crotalidae (pit viper) family of snakes, which includes rattlesnakes, copperheads, and cottonmouths. Rattlesnake bites deliver the most potent venom and are responsible for the majority of fatalities from snake bites; however, 10% to 50% of snake bites have been reported as dry bites. Acute first aid interventions include avoiding excessive activity of the affected site, immobilization in a neutral position, and expeditious transportation to a hospital. Antivenin is not recommended for dry bites (ie, no clinical evidence of envenomation) or if envenomation appears to be mild. Anaphylaxis and serum sickness are potential significant complications of equine antivenin. The general indication for antivenin administration is progressive venom injury. This is defined as worsening local injury (eg, swelling, pain, or ecchymosis), the onset of clinical coagulopathy, or the development of systemic effects including hypotension or changes in mental status. The patient should be monitored closely because the clinical presentation can change rapidly. Antivenin therapy should be instituted if signs or symptoms of envenomation develop or progress. Debridement of the bite site and suction therapy have not been shown to be beneficial in reducing the effects of envenomation and can cause additional necrosis to the tissue under the suction cup. Arterial tourniquets are contraindicated because they may worsen tissue ischemia and necrosis. Fasciotomy should be performed only for clinical signs and symptoms of compartment syndrome. Compartment syndrome and infection from extremity bites are extremely rare.

Answer 76

The correct response is Option D. Stevens-Johnson syndrome (SJS) and toxic epidermal necrolysis (TEN) are in the spectrum of the same disease process, characterized by a severe drug-induced immune reaction. The drug or its metabolite acts as a hapten and provides antigenic stimulation for a T-cell–mediated delayed hypersensitivity reaction. The list of offending medications is extensive and includes antibiotics, anticonvulsants and NSAIDs. Onset is within the first 8 weeks of starting the medication, and is characterized by fever, mucositis and a painful generalized vesiculobullous rash. Histology of skin specimens reveals keratinocyte apoptosis, full-thickness necrosis of the epidermis, and minimal dermal inflammation. Mucosal inflammation can involve any mucosal surface. Cutaneous involvement consists of blisters and erosions, with skin separation. Application of shear forces on the skin results in separation of the epidermis (Nikolsky sign). Skin separation of less than 10% of total body surface area is classified as SJS, greater than 30% of total body surface area as TEN, and 10 to 30% of total body surface area as SJS-TEN overlap. Multisystem organ dysfunction can occur. Treatment is supportive, with the best outcomes in patients treated early in a burn center. Intravenous corticosteroids are usually given, although their use is controversial. Mortality is 1 to 5% in SJS and 25 to 40% in TEN. Survivors are often left with skin scarring, mucosal strictures, and ocular complications. Toxic shock syndrome (TSS) is caused by toxin-producing strains of Staphylococcus aureus and Streptococcus pyogenes. The toxin acts as a super antigen and causes widespread immune stimulation. Staphylococcal Toxic Shock Syndrome can occur after surgical or traumatic skin break or from colonization of a foreign body. Onset is within 48 hours of surgery and consists of influenza-like symptoms, fevers, and shock. Multisystem organ failure can occur. Skin desquamation usually occurs 2 to 3 weeks later. Treatment consists of source control, antibiotic therapy, and in some cases, immunoglobulins. Acute generalized exanthematous pustulosis (AGEP) is a T-cell–mediated cutaneous drug reaction. Onset is usually within 48 hours and consists of fever, leukocytosis, and a rash consisting of many small sterile non-follicular pustules distributed predominantly on the trunk and intertriginous areas. Mucous membrane involvement is uncommon and occurs mostly in the lips and buccal mucosa. Internal organ involvement occurs in a minority of cases but can lead to multisystem organ dysfunction. Histology shows intracorneal, sub-corneal, and intraepidermal pustules and a dermal neutrophilic and eosinophilic infiltrate. Treatment is discontinuation of the offending drug, after which the condition quickly resolves. Prognosis is excellent. Drug reaction with eosinophilia and systemic symptoms (DRESS) is a severe drug reaction of unclear pathogenesis that is characterized by fever, hematological abnormalities (leukocytosis, eosinophilia), and internal organ dysfunction. Onset is typically 2 to 8 weeks after drug exposure. Antiepileptics are most commonly implicated, although a variety of drugs, including antibiotics, can be the causative agent. Cutaneous involvement consists of a morbilliform rash. Mucosal involvement is frequent. Facial edema can be severe. Blood leukocytes are markedly elevated, with 30% of cases having eosinophilia. Multisystem organ dysfunction can occur. Histopathology reveals a perivascular lymphocytic infiltrate in the papillary dermis and dermal edema with extravasated erythrocytes and eosinophils. Treatment consists of cessation of the offending drug, systemic glucocorticoids and supportive care.

Answer 77

The correct response is Option D. This patient's findings are most consistent with toxic shock syndrome. This condition should be suspected in any patient who has fever, hypotension, and erythroderma following surgery, trauma, or infection of structures related to the skin or nares. Symptoms include a temperature greater than 38.9%C (102%F), a diffuse macular rash, and a systolic blood pressure of less than 90 mmHg in adults or less than the fifth percentile for children younger than 16 years. Syncope and orthostatic hypotension are also common. Desquamation of the palms and soles typically occurs one to two weeks after the onset of illness. Appropriate management should include supportive treatment for multisystem organ involvement, antibiotics effective against Staphylococcus aureus, and identification and treatment of the focus of bacterial toxin production. Although the Staphylococcus organisms that produce toxic shock syndrome toxin typically do not produce purulent wounds and the surgical wound may appear normal, an undrained focus of infection may be present in the wound. Therefore, the wound should be debrided to locate any potential source of toxin-producing organisms and to provide tissue for bacterial culture. Acute gastroenteritis is associated with the abrupt onset of hypotension and abdominal symptoms such as nausea and diarrhea. Erythroderma is not an associated finding. Kawasaki disease is a multisystem disease typically seen in children younger than 7 years and characterized by prolonged fever, lymphadenitis, conjunctivitis, and erythema of the mucous membranes. Thrombocytosis and desquamation of the distal digits occur during the recovery phase. Hypotension is rare. Infection with Staphylococcus aureus and/or Streptococcus pyogenes is not associated. Patients with Stevens-Johnson syndrome have a systemic, widespread rash that also affects the mucous membranes. This condition can result from infection, illness, or an allergic reaction to medication. Systemic symptoms are typically severe. In patients with urosepsis, the onset of septic shock can be typically distinguished from toxic shock syndrome by the absence of erythroderma. Profuse watery diarrhea is uncommon in patients with urosepsis but occurs frequently in patients with toxic shock syndrome.

Answer 78

The correct response is Option E. This patient who has sustained a pit viper bite to the dominant right thumb requires immediate treatment involving fasciotomy, intravenous administration of antibiotics, and administration of pit viper antivenin. Approximately 98% of venomous snake bites are from pit vipers, and more than 70% of these bites involve the upper extremity. Pit vipers can be distinguished from other snakes by the presence of two retractable maxillae, each of which contains a fang for envenomation. In patients who sustain pit viper bites, immediate first aid should consist of patient reassurance, immobilization of the affected limb and placement of the limb on a level plane, and transportation to a hospital as soon as possible. Envenomation should be assumed with the presence of fang marks and rapid swelling of the extremity; broad-spectrum antibiotics should be administered immediately in the emergency department. Patients who have tense edema of the affected extremity and compartment pressures of greater than 30 mmHg should be diagnosed with compartment syndrome. Urgent fasciotomy should be performed. Because snake venom can greatly worsen myonecrosis and systemic findings, antivenin should be administered to any patient who has systemic symptoms of envenomation associated with increased laboratory values. Following administration of a test dose, five to 10 vials of snake antivenin are typically administered in patients who do not exhibit allergic sensitivity. A central line should be placed and emergency resuscitation should be available. The administration of as many as 20 vials of antivenin may be required in patients who have extreme abnormalities on laboratory evaluation. Application of ice will result in vasoconstriction, ischemia, and tissue necrosis. Incision and suction drainage of the bite wound should be performed within 15 minutes of the bite.

Answer 79

The correct response is Option C. This 6-year-old boy has purpura fulminans, an uncommon illness that typically affects young children but can also occur in adults. Purpura fulminans often develops in association with a predisposing condition. It manifests as severe hemorrhage and necrosis of skin associated with disseminated intravascular coagulation. Affected patients have petechial rashes, which progress to confluent areas of ecchymosis, and then to necrotic, hard, full-thickness eschar. Bilateral symmetric gangrene of the extremities necessitates amputation in as many as 20% of patients. Reconstructive procedures, including free tissue transfer, are frequently required to resurface necrotic areas and salvage extremities with exposed joints. Septic shock and organ failure may also result. Mortality rates have been reported to be as high as 60%. Purpura fulminans is associated with endotoxin-producing bacteria. Although Neisseria meningitidis is the most common causative organism, Streptococcus pneumoniae, Haemophilus influenzae, and Rickettsia have also been implicated. The mechanism of this condition is believed to be liposaccharide-mediated endothelial damage caused by bacteria, leading to decreased serum levels of proteins C and S. Skin necrosis results from a low-flow coagulative state and microemboli. Management of affected patients includes general hemodynamic support, intravenous administration of an appropriate antibiotic, wound care, eventual soft-tissue reconstruction, and amputation when necessary.

Answer 80

The correct response is Option C. This patient has a dystrophic nail resulting from a fungal infection (onychomycosis). The diagnosis of onychomycosis can be confirmed by positive findings on fungal culture. Fungal infections are the underlying cause of dystrophic nails in approximately 50% of affected patients; the remaining 50% are caused by other factors, including psoriasis, lichen planus, and trauma. Although they are more common in the foot, fungal infections can cause functional and aesthetic deformities in the fingernails. In the past, long-term administration of antifungal agents was recommended; however, this treatment course was associated with significant toxicity, requiring monitoring of hepatic function, and often disappointing results. More recently, terbinafine and itraconazole have offered new treatment options. This agents are administered for six weeks, and hepatic function is monitored only in those patients who have a history of hepatitis, liver disease, or heavy alcohol use. However, adverse effects associated with terbinafine use include Stevens-Johnson syndrome, neutropenia, hepatotoxicity, hepatic failure, erythema multiforme, toxic epidermal neurolysis, and anaphylaxis. In addition, terbinafine is far more costly than previously used antifungal agents. Topical or oral administration of antibiotics would not be expected to improve this fungal infection. In addition, topical antibiotics may aggravate the nail matrix. Resection of the sterile matrix and replacement with a graft is associated with a high incidence of recurrence and morbidity. Removal of the nail would not eliminate the fungal infection within the underlying matrix.

Answer 81

The correct response is Option D. Necrotizing fasciitis is a severe soft-tissue infection affecting the skin, subcutaneous tissue, and fascia. It characteristically spares the underlying muscle, progresses quickly, and is associated with high morbidity and mortality rates and severe systemic sepsis. The inciting event is often trauma, even minor trauma and small puncture wounds, but hematogenous spread is also a recognized etiology. The vast majority of patients have some form of chronic debilitating disease that weakens the immune system. Diabetes mellitus appears to be the most common disease, but these may include substance abuse and renal failure. These patients are at higher risk for increased mortality. Two types of necrotizing fasciitis have been described. Type I are mixed aerobic and anaerobic infections, with facultative anaerobic bacteria and non-group A streptococci being present. This is the most common type and is present in about 75% of cases. Type II infections are monomicrobic and are caused by group A Streptococcus species alone or in combination with staphylococcal species. For this reason, antibiotic coverage should be broad. The disease progresses quickly but does evolve through several stages. Initial symptoms include tenderness, erythema, edema, warm skin, and fever; however, symptoms may vary depending on patient characteristics. Initial lab findings may include leukocytosis, thrombocytopenia, and hyperkalemia, but these are variable. When critical skin ischemia occurs, blisters or bullae are formed. In the late stage, lesions turn black and necrotic and are anesthetic as the nerves become involved. Diagnosis begins with a high clinical suspicion in all patients, particularly those with risk factors. Appropriate treatment is surgical debridement, broad-spectrum intravenous antibiotic therapy covering gram-positive, gram-negative, and anaerobic organisms, and careful monitoring and correction of fluid and electrolytes in an intensive care setting. Most authorities agree that hyperbaric oxygen is to be recommended for the treatment of necrotizing fasciitis as an adjunct, if facilities are available and there is no delay in surgical debridement. However, most studies regarding the efficacy of hyperbaric oxygen are anecdotal with a distinct lack of properly designed prospective randomized controlled trials. Mortality rates are reported to be 10 to 75% and are increased in patients with underlying immune compromise, delayed treatment, or involvement of the chest wall.

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Infections - Soft Tissue - Hand Flashcards

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